There is an information processing apparatus that includes system control boards that control computer hardware, function as system control devices and form a redundant configuration. The information processing apparatus is a server that may be used for various usage purposes, for example. In addition, the information processing apparatus is a system that achieves high reliability since the information processing apparatus includes the system control boards that form the redundant configuration.
In the information processing system, one of the system control boards has a central processing unit (CPU) and a memory (storage device). The one of the system control boards controls computer hardware components such as a system board (for performing arithmetic processing), a crossbar board (for transferring data between the system control boards) and an input/output (I/O) board (for performing input/output control of a hard disk drive, a network, and the like). The one of the system control boards manages and monitors the computer hardware components. The other system control board is in a standby state in case the one of the system control boards, which controls the information processing apparatus and is in an operating state, fails.
However, when the server switches the system control boards during transfer of data between at least one of the computer hardware components (such as the system boards, the crossbar board and the I/O board) and a direct memory access (DMA) master (DMA controller) mounted on the system control board that is in the operating state, the following phenomenon occurs. The state of a DMA master that is mounted on the system control board that is changed from the standby state to an operating state owing to the switching of the system control boards is different from the state of the DMA master mounted on the system control board that is changed from the operating state to a standby state owing to the switching of the system control boards.
Thus, the system control board that has been changed from the standby state to the operating state may not take over the operating state of the system control board that has been changed from the operating state to the standby state.
Japanese Laid-open Patent Publication No. 2002-049502 discloses a technique related to an information processing system that has control mechanisms that form a redundant configuration.